How to Prepare for A-Level Physics Practical Exams: Rules for the Cambridge Paper 3 Practical, and Edexcel Units 3, 6, and the 16 Core Practicals

For A-Level Physics practicals, Cambridge and Edexcel have the most significant differences in their exam formats: Cambridge Paper 3 requires students to complete two experiments in a lab within two hours, handling all measurements, graphing, and uncertainty calculations independently; Edexcel's Unit 3 and Unit 6 are written exams focusing on the design, measurement, and data processing of 16 core experiments. We have already covered Cambridge Paper 5 (practical design on paper) for the A Level stage in detail in Aiming for an A* in A-Level Physics. This article focuses on Cambridge Paper 3 and Edexcel's two practical units. For the overall structure, see How A-Level Physics is Tested. For Chemistry and Biology practicals, see articles 183 and 184.

1. Which Papers Include Practicals?

The Cambridge syllabus recommends that students spend at least 20% of their study time on hands-on practical work, either individually or in groups; watching demonstrations does not count.

2. Cambridge Paper 3: Two Questions, 1 Hour and 20 Marks Each

• Question 1: Collect data, plot graphs, and draw conclusions;
• Question 2: Collect data and draw conclusions, not necessarily plotting graphs. The experimental method provided in the question is inherently flawed, requiring students to evaluate the method and suggest improvements;
• The two questions cover different areas of physics, and no prior knowledge of the relevant theory is required.

Mark Allocation

The remaining 3 marks for each question are distributed among these skills and vary each time. This table highlights the focus of the two questions: Question 1 tests measurement and graphing, while Question 2 tests evaluation and improvement.

Measurement: Instruments Specified in the Syllabus

• Millimeter ruler, protractor, electronic balance, newton meter, analog or digital meters, measuring cylinder, vernier caliper or digital caliper, micrometer, thermometer;
• Use a stopwatch to measure time intervals, including determining the period by measuring the total time for multiple consecutive oscillations;
• Must be able to read both analog scales and digital displays;
• Setting up apparatus: Students who need the invigilator's help to set up the apparatus will not receive full marks for "successful data collection"; under no circumstances may the invigilator help with data processing, analysis, or evaluation;
• Quality of data: Measurements must be accurate, and students should aim for the largest possible range of values within the limits of the equipment or the question. Examiners may award marks based on the scatter of points on the graph or by comparing them with data provided by the invigilator.

Tables and Records: Rules in the Syllabus

• All data must be in a single table. Draw the table before taking measurements; do not copy data in afterward. The table should include columns for both raw data and calculated values;
• Column headings must include the physical quantity and unit: The syllabus example for current in milliamperes is "I / mA". "I in mA", "I (mA)", or "current / mA" are also acceptable, but "I mA" or just "mA" is not allowed;
• Consistent precision for raw data in the same column: For example, if a length is recorded to the nearest millimeter, all entries in that column must be to the nearest millimeter. The precision must match the instrument; recording a distance measured with a millimeter ruler as "2 cm" or "2.00 cm" is inappropriate;
• Significant figures: For quantities calculated from measured values (excluding addition and subtraction), use the least number of significant figures, n, among the measured values, and give the result to n or n+1 significant figures. Syllabus example: if voltage is measured to 2 significant figures and current to 4, the calculated resistance should be given to 2 or 3 significant figures, not 1 or 4.

Graphing: Rules in the Syllabus

• Axis labels must include the physical quantity and unit, following the same rules as table headings;
• Data points must cover at least half the grid in both directions; use a non-zero origin if necessary;
• Scales must be easy to read, e.g., 2 cm per major grid line representing 1, 2, or 5 units; each axis must have evenly spaced numerical labels at least every 2 cm;
• Plot points with a precision better than 1 mm, using a thin cross or a dot with a circle; the diameter of the dot must be less than 1 mm;
• Draw a line of best fit (straight or curved) with points evenly distributed on both sides; the line must be thin, continuous, less than 1 mm thick, and have no kinks; one point may be identified as an anomaly and ignored when drawing the line, but it must be circled or labeled;
• Be able to draw a tangent to a curve.

Analysis and Evaluation

• Reading graphs: Relate a straight line to y = mx + c and write expressions equal to the gradient or intercept; when calculating the gradient, the two points chosen must be more than half the length of the drawn line apart; if the intercept cannot be read from a graph with a non-zero origin, substitute the coordinates of a point on the line and the gradient into y = mx + c to find the intercept;
• Uncertainties: Estimate the absolute uncertainty of a measurement, and convert between absolute and percentage uncertainties; for repeated measurements, the absolute uncertainty is half the range of the readings;
• Testing relationships: Calculate the percentage difference between two values of a constant, compare it with the percentage uncertainty given in the question, and draw a conclusion accordingly;
• Identifying limitations: State the limitations of the experimental method and the main sources of uncertainty. For the uncertainty in a measured quantity, specify which quantity it is and why it is uncertain;
• Suggesting improvements: Must be realistic, feasible in a school lab, and can involve changing equipment or methods, but cannot change to a completely different experiment; improvements that could already be achieved using the equipment provided and following the question's instructions typically do not score marks.

3. Cambridge Paper 5: A Brief Review

Paper 5 is taken at the A Level stage and consists of two 15-mark questions: Question 1 involves planning an experiment (with a diagram and a long paragraph of text), and Question 2 provides an equation and data to find a constant and estimate uncertainty, requiring error bars and a worst acceptable line. See Part 4 of Aiming for an A* in A-Level Physics for details. The solid graphing and uncertainty skills practiced in Paper 3 form the foundation for Paper 5.

4. Edexcel Unit 3 and Unit 6: Written Practical Exams

Both units are 1 hour 20 minutes, 50-mark written exams, available in January, June, and October. Each paper allocates at least 20 marks to Level 2 or above mathematical skills. The structure of the two papers is similar, divided into three sections:

The syllabus gives an example of a log-log graph: investigating the relationship between the pressure and volume of a fixed mass of gas at constant temperature by plotting a log-log graph to determine the relationship between the two.

16 Core Practicals

The syllabus states that the theory units (Units 1, 2, 4, and 5) will also test practical knowledge, both in the context of these 16 core practicals and in new practical contexts. For the planning questions in the practical units, the experiments are specified by the exam board. Therefore, you cannot just memorize these 16 practicals.

5. How to Prepare

Here are some practical tips based on experience.

Cambridge Candidates

1. Practice instrument readings: Read vernier calipers, micrometers, and analog meters quickly and accurately; count multiple oscillations when measuring the period;
2. Practice building circuits yourself: The syllabus explicitly states that marks will be deducted if you need help setting up the apparatus;
3. Make graphing rules a habit: Check scales, plotting points, lines of best fit, and gradient triangles against the syllabus point by point;
4. Prepare a "Limitations-Improvements" table for Question 2: List the main sources of uncertainty and feasible improvements for common experiments (e.g., timing errors → use light gates or video analysis; parallax errors → read at eye level or use markers). For each point, specify exactly what quantity is being measured and why it is inaccurate;
5. Manage your time: You have 1 hour per question; do not let measurements drag on so much that you have no time to plot graphs;
6. Private candidates: Paper 3 must be taken in the exam center's laboratory. Confirm that the center can arrange this before registering.

Edexcel Candidates

1. Take notes on each of the 16 core practicals: Equipment and resolution, measurement methods, control variables, graphing methods, sources of uncertainty and improvements, and safety;
2. Focus on the new requirements for Unit 6: Logarithmic graphs, combined uncertainties, and the distinction between precision and accuracy;
3. Practice "spot the error" questions: The Implementation and Measurement sections often provide flawed tables and data. You need to quickly identify errors in significant figures, units, and anomalous readings.

Conclusion

Scoring well in A-Level Physics practicals relies on standardization and proficiency: Cambridge Paper 3 has explicit rules for readings, table headings, graphing, significant figures, and improvement suggestions, while Edexcel tests your ability to apply the methods and uncertainty analysis of the 16 core practicals to new contexts. Turn the syllabus rules into habits, and you will steadily secure your practical marks. If you need A-Level Physics tutoring or specialized practical training, feel free to chat with our teachers.

Verification note: This article was verified in September 2026. The format of Cambridge 9702 Paper 3, the structure of the two questions, mark allocation, apparatus, table and graphing rules, examples of significant figures, uncertainties, requirements for limitations and improvements, and the recommendation of 20% practical time are sourced from Cambridge International's Physics 9702 syllabus for 2025, 2026 and 2027; the weightings for Paper 3 and Paper 5 are also from this syllabus; the content of Paper 5 was verified in article #177 on this site. The format, duration, marks, weightings, exam sessions, mathematical requirement, requirements for the Planning/Implementation/Analysis sections, and the 16 core practicals for Edexcel Unit 3 and Unit 6 are sourced from the Pearson IAL Physics Syllabus (3rd Edition). The preparation methods are our practical recommendations based on experience.

References:

• Cambridge International: AS & A Level Physics (9702)
• Pearson: International Advanced Level Physics